论文标题
精确的早期宇宙热力学简单：$ n _ {\ rm eff} $和中微子在标准模型及其他
Precision Early Universe Thermodynamics made simple: $N_{\rm eff}$ and Neutrino Decoupling in the Standard Model and beyond
论文作者
论文摘要
有效相对论中微子物种数量和原始元素丰度数量的精确测量需要对标准模型及更高版本中早期宇宙可观察到的准确的理论预测。鉴于对早期宇宙的热历史进行准确建模的复杂性，在这项工作中，我们扩展了作者提出的一种先前的方法，以获得简单，快速，准确的早期宇宙热力学。该方法基于以下近似值：所有相关物种都可以通过温度和化学电位为特征的热平衡分布函数描述。我们将方法应用于标准模型中的中微子解耦，并找到$ n _ {\ rm eff}^{\ rm sm} = 3.045 $ - 结果与先前的先进计算非常吻合。我们应用方法在存在非常光的情况下研究宇宙的热历史（$ 1 \，\ text {ev} <m_ϕ <1 \，\ text {mev} $）和弱耦合（$λ\ simssim 10^{ - 9}} $ scalar。我们发现我们的结果与解决确切的Liouville方程式的解决方案非常同意。最后，我们发布了一个代码：NUDEC_BSM（以Mathematica和Python格式使用），可以在标准模型及更高版本中准确有效地解决中微子的解次：https：//github.com/migeleaub.com/migelealea/nudec_bsm。
Precision measurements of the number of effective relativistic neutrino species and the primordial element abundances require accurate theoretical predictions for early Universe observables in the Standard Model and beyond. Given the complexity of accurately modelling the thermal history of the early Universe, in this work, we extend a previous method presented by the author to obtain simple, fast and accurate early Universe thermodynamics. The method is based upon the approximation that all relevant species can be described by thermal equilibrium distribution functions characterized by a temperature and a chemical potential. We apply the method to neutrino decoupling in the Standard Model and find $N_{\rm eff}^{\rm SM} = 3.045$ -- a result in excellent agreement with previous state-of-the-art calculations. We apply the method to study the thermal history of the Universe in the presence of a very light ($1\,\text{eV}<m_ϕ< 1\,\text{MeV}$) and weakly coupled ($λ\lesssim 10^{-9}$) neutrinophilic scalar. We find our results to be in excellent agreement with the solution to the exact Liouville equation. Finally, we release a code: NUDEC_BSM (available in both Mathematica and Python formats), with which neutrino decoupling can be accurately and efficiently solved in the Standard Model and beyond: https://github.com/MiguelEA/nudec_BSM .
